Model Output Discussion October 2012

[Frosty.]

The Gfs 06z operational run ends up being fairly anticyclonic, especially for southern britain but occasionally for all areas but the northern half of the uk is windier and more changeable at times, during the anticyclonic spells it looks like there would be some chilly nights with a touch of frost and some overnight mist and fog but pleasantly warm daytime in the afternoon sunshine, especially during the high pressure pattern shown for the early to middle part of next week although it does look briefly more unsettled to the southwest. The high is eventually pushed away southeast into mainland europe by the end of next week but is soon replaced by atlantic high pressure, then the south continues to have higher pressure for most of the time but sometimes breezy and cloudier. The flood of arctic air across norway in FI is interesting, but on this run has negligable impact on the uk apart from the far north and east which briefly looks cooler and more showery later in FI.

Edited October 4, 2012 by Frosty039

[Iceaxecrampon]

_{The "cooldown" starts - more cherry picking but - hey! - its a model discussion whether or not they are proved to be correct - maybe FI charts should be exempt but where is the fun value in that?}

_IAC

[summer blizzard]

Other than a breif interlude of mild uppers on Monday and Tuesday i see no real signs of warmth and if anything it looks pretty cool at the surface.

A far cry from 2011.

[Summer Sun]

After a brief warm up early next week things turn cooler again by next weekend with a chance of snow for parts of Scotland

High pressure then builds again temps are nothing special but the cold air gets shifted away, so and precipitation would be rain

High pressure continues to stay put

By the end of FI the high pressure slowly moves west allowing a cold northerly wind to set up

Day maxes are low for the time of year epically for the north

Edited October 4, 2012 by Summer Sun

[Frosty.]

The Gfs 12z operational is showing a nice spell of high pressure developing during next week after an unsettled start in the south and southwest, with most of the uk becoming settled for a while with light winds and sunny weather but chilly overnight with mist and fog patches but then later next week the high loses it's grip as low pressure to the northwest brings unsettled cooler weather southeast across all areas with a mix of sunshine and showers after the main front has cleared through. Atlantic high pressure then pushes east across the southern half of the uk but it remains generally more changeable across the north with stronger winds, then there are signs that soon after mid month it could become more generally unsettled and rather cool and the gfs 12z shows a fairly cyclonic pattern towards the end of the run.

[IDO]

GFS Op run has been going with HP next week for many runs, apart from the odd outlier. If anything it's 12z run is even more progressive with the high, especially and more so it's ensembles. ECMW have been going with a trough and lows till this morning when they started a rearguard action edging in with the HP. Tonight's 12z should reinforce this about turn. The GFS to me have been seeing changes better than ECMW lately.

Again in late FI, similar to the 0z run, GFS show's a possible favorable blocking pattern:

12z run:

http://www.weatheron...=0&WMO=&PERIOD=

0z run:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gfs&MODELLTYP=1&BASE=201210040000&VAR=pslv&HH=384&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

The second half of October showing potential for a colder spell, certainly more promising than last year.

Edited October 4, 2012 by i'm dreaming of...

[cooling climate]

Just for fun check out the CFS 12z run its insane for cold and snow.

Do not know whether it should be in this thread or not.

[Gibby]

Hi Folks. Here's my take on the 12z outputs from GFS, UKMO and ECM tonight.

All models show a wave depression run East across Southern Britain overnight. It then trails back for a re-run tomorrow night while Northern regions continue to lie in a weak showery Westerly flow. Saturday shows a ridge of High pressure cross Britain from the West giving a bright and dry day on Saturday in light winds. A cold night saturday night will be followed by a decent Sunday too in more Northern and Eastern regions while the South and West see Low pressure edging up from the SW with rain bearing fronts reaching the mainland by afternoon.

GFS shows Low pressure over the South with rain and showers in tow. A High pressure ridge in the NW spreads SE on Tuesday squeezing the life out of the Low pressure leaving many areas dry if rather cloudy. Through the middle of the week the ridge holds on with another dry bright day. By Thursday a cold frontal trough is shown to cross East with a band of rain for all. Thereafter, a typical mid Autumn spell of changeable Atlantic based weather is shown with rain or showers at times as Low pressure passes to the North of Britain. As always the most rain and wind would be likely in the North while temperatures remain close to the October normal.

The GFS Ensembles show a typical sine wave pattern for Northern locations indicative of an Atlantic dominated pattern of trough, ridge, trough sequence. In the South too changeable weather is shown with temperatures at 850's levels hovering slightly either side of the long term mean throughout meaning at the surface no particularly mild or cold spells seem likely.

The Jet Stream is shown to broaden as it continues it's track East over the UK in the next 72hrs. Soon after the Northern section of the flow strengthens and disengages from the Southern portion leaving the Northern portion to become the dominant flow blowing way North over Iceland then SE down the North Sea. The Southern portion by this time disintegrates entirely.

UKMO for noon on Wednesday shows a Low pressure belt stretching from a position West of Iceland to Southern England. There would be rain or showers in all areas from this pattern.

ECM shows Low pressure filling near Southern England early next week with a weak High pressure slipping down from the NW. Rain in the South would lessen in intensity and frequency with time with drier conditions spreading down from the NW. Later in the week Low pressure North of Scotland takes control carrying rain bands East across Britain, heaviest in the North. Towards the end of the run High pressure builds strongly in mid Atlantic with a cold Northerly flow with showers blowing down over the UK

In Summary a changeable weather pattern remains the outlook tonight. It is hard to pick details out as the models differ in the way things go next week but all offer some rain at times for most areas with the emphasis on amounts going to be greatest in the North. Some drier and brighter spells look likely too with temperatures never that far from the seasonal normal at the surface although if the ECM operational came to pass it would turn quite chilly from the North towards 10 days.

[syed2878]

hi people today's noaa's discussion. here's what they had to say.

PRELIMINARY EXTENDED FORECAST DISCUSSION.

VALID 12Z MON OCT 08 2012 - 12Z THU OCT 11 2012

...RELATIVELY COOL AND UNSETTLED CONDITIONS ACROSS MUCH OF THE

LOWER 48...

GENERAL FLOW PATTERN

====================

THE GUIDANCE REMAINS IN GENERAL AGREEMENT THAT THE REX BLOCK IN

THE EASTERN PACIFIC WILL TRANSFORM INTO A FULL LATITUDE RIDGE

/WITHIN A TILTED OMEGA BLOCK/ WAVERING AROUND THE 130TH MERIDIAN

/OFFSHORE THE WEST COAST OF THE UNITED STATES AND NEAR THE WEST

COAST OF CANADA/. THE SOUTHERN COMPONENT OF THE REX BLOCK... THE

UPPER LOW... IS FORECAST TO MOVE FROM THE SUBTROPICAL PACIFIC INTO

THE SOUTHWEST CONUS. TELECONNECTIONS WITH THE UPPER RIDGE SUPPORT

BROAD TROUGHING DOWNSTREAM CENTERED NEAR 90W /GREAT LAKES TO

MISSISSIPPI VALLEY/ WITH PERIODIC CLIPPER SYSTEMS EXPECTED TO

SWEEP DOWN TOWARDS THE US/CANADIAN BORDER TO REINFORCE THE TROUGH.

STANDARDIZED ANOMALIES OF THE 500MB HEIGHTS ASSOCIATED WITH THE

RIDGE/TROUGH COUPLET ARE ON THE ORDER OF +2.5/-3.0 FROM THE MEAN

FOR THE FIRST THIRD OF OCTOBER... SO A COOLER THAN AVERAGE FEW

DAYS IS IN STORE FOR ESPECIALLY THE CENTRAL UNITED STATES.

　

MODEL PREFERENCES

=================

THE DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE WERE IN GOOD

AGREEMENT... INCLUDING MANY SMALLER DETAILS. THE MODELS SHIFTED

THE EASTERN PACIFIC RIDGING SLIGHTLY WESTWARD WHICH BROADENED

TROUGHING DOWNSTREAM OVER THE CONTINENT /SEEN IN THE ECMWF

YESTERDAY/. THE 00Z GFS AND GEFS MEMBERS APPEAR TO MOVE THE

EASTERN PACIFIC RIDGING INTO WESTERN CANADA TOO QUICKLY GIVEN THE

AMPLIFIED FLOW WHICH CAUSES A CORRESPONDING SHIFT IN THE TROUGH

DOWNSTREAM. THE 06Z RUN WAS AT LEAST A BIT SLOWER OVER THE EASTERN

CONUS TO MATCH THE ECMWF... WHICH ALSO LIES CLOSE TO THE LAGGED

AVERAGE ECMWF FORECAST. THE PRESSURES WERE BASED ON A 40/30/30

BLEND OF THE 00Z UKMET/00Z ECMWF/00Z GFS THROUGH TUESDAY BEFORE

SWITCHING TO A 40/60 BLEND OF THE 00Z GFS/00Z ECMWF WEDNESDAY AND

A 50/50 BLEND OF THE 06Z GFS/00Z ECMWF NEXT THURSDAY. THIS

SOLUTION KEPT VERY GOOD CONTINUITY WHEN COMPARED TO THE PREVIOUS

TWO DAYS OF HPC FORECASTS.

　

WEATHER IMPACTS

===============

THE PACIFIC NORTHWEST SHOULD REMAIN HIGH AND DRY UNDER THE AEGIS

OF A WARM CORE RIDGE THROUGH MUCH OF THE PERIOD... WITH THE NEXT

THREAT OF RAIN POSSIBLY NOT UNTIL LATE NEXT THURSDAY.

DOWNSTREAM... THE AMPLITUDE OF THE MID-CONTINENTAL TROUGH IS

EXPECTED TO KEEP CONDITIONS COOL OVER MUCH OF THE LOWER 48.

TEMPERATURES MAY BE UP TO 20F DEGREES BELOW NORMAL AT THE START OF

THE PERIOD BEFORE MODERATING IN TIME. A SHORTWAVE INITIALLY OVER

THE MIDWEST WILL MOVE EASTWARD... QUICKLY SPREADING PRECIPITATION

ACROSS THE MID-ATLANTIC/NEW ENGLAND STATES SUNDAY. AN EARLY-SEASON

CLIPPER SYSTEM MOVING OUT OF WESTERN CANADA COULD BRING A SECOND

CHANCE FOR RAIN/SNOW TO NORTH DAKOTA AND MINNESOTA BETWEEN SUNDAY

NIGHT AND TUESDAY NIGHT... WITH COLD RAINS EXPECTED TO SPREAD

ACROSS THE GREAT LAKES MONDAY INTO LATE TUESDAY.

THE CLOSED LOW MOVING INTO CALIFORNIA LATE MONDAY WILL COOL OFF

PORTIONS OF THE WEST AND MOJAVE DESERT AS IT PROGRESSES THROUGH

THE REGION. THE SYSTEM COULD LEAD TO UPSLOPE AND INSTABILITY

PRECIPITATION UNDER THE UPPER-LEVEL COOL POOL ACROSS THE SISKIYOU

AND SIERRA NEVADA RANGES SUN/MON AND THEN INTO NV/AZ/UT TUE-WED.

GULF MOISTURE WILL INCREASE THROUGH THE LOWER MS VALLEY AHEAD OF

THE UPPER LOW AS A SHORTWAVE IN THE NORTHERN STREAM MAY TAP INTO

THIS AND SPREAD RAINFALL EASTWARD THROUGH THE OHIO VALLEY/GREAT

LAKES/NORTHEAST. A SECOND CLIPPER SYSTEM WAITS IN THE WINGS ACROSS

WESTERN CANADA TUE-WED AND SHOULD PASS NORTH OF THE CENTRAL

US/CANADIAN BORDER WEDNESDAY INTO NEXT THURSDAY... POSSIBLY

LEADING TO A WINTRY MIX NEAR THE CENTRAL US/CANADIAN BORDER AND

LAKE SUPERIOR WEDNESDAY NIGHT INTO THURSDAY.

ROTH.

Last Updated: 943 AM EDT THU OCT 04 2012.

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

Mod's again if this post is in the wrong thread plz remove thx.

[Iceni]

GFS Op run has been going with HP next week for many runs, apart from the odd outlier. If anything it's 12z run is even more progressive with the high, especially and more so it's ensembles. ECMW have been going with a trough and lows till this morning when they started a rearguard action edging in with the HP. Tonight's 12z should reinforce this about turn. The GFS to me have been seeing changes better than ECMW lately.

Again in late FI, similar to the 0z run, GFS show's a possible favorable blocking pattern:

12z run:

http://www.weatheron...=0&WMO=&PERIOD=

0z run:

http://www.weatheron...=0&WMO=&PERIOD=

The second half of October showing potential for a colder spell, certainly more promising than last year.

Just like Piers predicted in the Express — a week ago.

[winterof79]

Just for fun check out the CFS 12z run its insane for cold and snow.

Do not know whether it should be in this thread or not.

I am interested early this year...for some reason..

http://www.wetterzen...s/Rtavn3001.png

That is becoming a trend CC.

Edited October 5, 2012 by winterof79

[IDO]

Next week HP battles LP and seemingly wins (0z GFS). Would not have thought it would be a dry scenario as LP mixes in with the HP.

By T174 we have a complex setup:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gfs&MODELLTYP=1&BASE=201210050000&VAR=pslv&HH=174&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

So not sure confidence is high from here. GFS has a cool high winning out and by late in FI (third run in a row) this:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gfs&MODELLTYP=1&BASE=201210050000&VAR=pslv&HH=384&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

Not sure if its a toppler but with the trough over the US eastern seaboard and Atlantic high filling in, there are signs for a colder spell. Long way out so...

[Gibby]

Good morning. Here's my look at the 00zs this morning. There are differences from quite early on so individual reports today.

GFS shows a complex and rippling trough near Southern England which persists no further away then the English Channel for the period until Sunday when it moves its way slowly North. Further north the weak and showery Westerly flow is replaced by high pressure moving slowly ESE across Scotland with fine and dry weather more likely here while Southern England sees rain at times. GFS then continues through next week with High pressure at first glance in control but in reality a lot of cloud and some rain would be likely, especially near Southern and Western Britain as the trough to the West fills slowly. Later in the week a col develops as the remains of the trough cross east with Atlantic High pressure building to the west pushing a ridge East and turning winds NE in the South. Any remaining rain would likely be over by then but skies look like remaining quite cloudy in the South at least. FI this morning is totally dominated by a strong Atlantic anticyclone bringing chilly NW winds and plenty of dry weather away from the far North and East before the trend towards cold and unsettled weather takes over for all by the end of the run.

The GFS Ensembles show a dry spell for the North and East while Southern areas see rain in abundance over the next 24-48hrs before conditions moderate to changeable conditions. thereafter. The operational was a cold outlier in the second half of the run though the mean for 850's does drop to just below the long term mean later in the run for locations North and South.

The Jet Stream is shown to split in a few days time with the Northern arm superseding the Southern one, weakening it entirely away with time. The northern arm takes up residence way up over Iceland as we move into next week and then SE towards Denmark.

UKMO also shows a trough close to Southern Britain through the weekend with heavy rain at times before it brings the offending trough NE over the UK on Monday and Tuesday with a rather mild SW flow with heavy showers the order of the days of Monday and Tuesday. It then moves on to shows Low pressure over Iceland with a West to Northwest flow developing over Britain by midnight on Thursday. Troughs embedded in the flow would ensure rain at times through this day.

ECM looks quite similar to UKMO over the weekend though is slower in bringing in the rain from the SW keeping many Northern and eastern areas dry until Monday. The same showery SW flow that UKMO shows evolves then for a day or too at 144hrs a large Atlantic High steers NW winds down over the UK with troughs too. These will be most active in the North and East with the SW seeing a lot of dry if rather cloudy weather in near normal temperatures. Northern parts could become rather chilly for a while though. Very late in the run the Atlantic high slips south allowing winds to back Westerly with the emphasis of rain shifting to Northern and Western parts.

In Summary it looks like a large and significant Atlantic high is likely to become dominant in the synoptics of the coming few weeks. It looks too far out in the Atlantic for any direct effect on our weather but will deliver winds from a NW or Northerly quarter and whilst some models hold it closer in to the UK with consequently a lot of dry weather GFS in particular take it further out with time with cold and unsettled conditions spreading into the UK late in the run. Lots to play for in subsequent runs as there are differences in the models from a very early stage this morning.

[summer blizzard]

I am interested early this year...for some reason..

http://www.wetterzen...s/Rtavn3001.png

That is becoming a trend CC.

Thats a shockingly dead Jet Stream for October.

[Frosty.]

There are large differences between the gfs and ecm 00z ens mean as early as T+120 hours (earlier actually) so FI starts around T+72 to 96 range IMO, the gfs is showing an anticyclonic spell for much of next week whereas the ecm soon turns unsettled from the northwest so it's hard to know at this stage what will happen but there is growing support for a rather cold and unsettled spell with nw'ly winds, the gfs ens mean indicates a cold n'ly with wintry showers on northern hills before atlantic high pressure topples into the uk but that's outside the reliable timeframe. The further outlook suggests to me that high pressure will probably become centred close to the southwest of the uk with a moist wsw'ly flow and low pressure to the northwest or north.

Edited October 5, 2012 by Frosty039

[Gavin P]

Hi everyone,

Here's todays 8-10 day model based musing video - Becoming Cold For Mid October?

http://www.gavsweathervids.com

Signs of a temperature drop on the way for mid month with temps maybe struggling to get into double figures away from the south and the first proper widespread frosts of the season..

Enjoy

[Frosty.]

Imagine the meltdown on here if this chart appeared in winter, it's wasted in mid october but the 6z is showing some major build up of cold to the north and northeast with frigid arctic air but for the first half of the gfs 6z it's a run which becomes fairly benign with relatively high pressure and a slack looking pattern by the middle of next week, then a coolish nw'ly with some showers before high pressure builds strongly further into FI with a scandi high, even some hp retrogression possibly opening the door for some of that arctic air to maybe flirt with the eastern side of the uk later but it's absolutely nothing like the 00z gfs ens mean showed.

[Gavin P]

Yes Frosty, certainly interesting trends/patterns from GFS in FI today if not particularly interesting weather.

[Frosty.]

Yes Frosty, certainly interesting trends/patterns from GFS in FI today if not particularly interesting weather.

Yes Gavin, I like some of the charts the gfs is churning out as they have a more seasonal flavour, it's nice to see the build up of frigid arctic air being bottled up across arctic regions, the sea up there will soon be under ice and any northerly we get after mid october will then have more bite.

[johnholmes]

but there is growing support for a rather cold and unsettled spell with nw'ly winds,

This is confirmed by the 3 anomaly charts at 500mb, all show over the past 2-3 days a 500mb flow from n of west, not total agreement on the position of the trough to the east, but it gives an unsettled feel to what can be expected in the 6-15 day time frame, and not warm for sure. As the last bit from frosty suggested(not copied here) there is the probability of the upper ridge and consequently a surface ridge settling in close the SW of the UK in that time frame.

[Methuselah]

This is confirmed by the 3 anomaly charts at 500mb, all show over the past 2-3 days a 500mb flow from n of west, not total agreement on the position of the trough to the east, but it gives an unsettled feel to what can be expected in the 6-15 day time frame, and not warm for sure. As the last bit from frosty suggested(not copied here) there is the probability of the upper ridge and consequently a surface ridge settling in close the SW of the UK in that time frame.

So it might even snow in Carlisle?

[snow drift]

So it might even snow in Carlisle?

This has to be the first post this season , will it snow IMBY, and from one of the NW Team!!!!!!!!!!!! Love it!!!!!!!!

[Andy Bown]

This has to be the first post this season , will it snow IMBY, and from one of the NW Team!!!!!!!!!!!! Love it!!!!!!!!

It's not about his back yard! It's an old NW joke after a member who always asked about snow in Carlisle.

[Cloud 10]

So it might even snow in Carlisle?

It might snow in Cardiff as well,but only sleet in Telford..

[phil nw.]

Just a little observation reflecting the cooling of the Northern hemisphere.

GFS12z at T120rs shows the placement of upper troughs advecting some cold uppers south across continental landmasses,

A reminder that Winter for some of these areas is almost here-some freezing 2m temperatures moving in.

Edited October 5, 2012 by phil n.warks.